Remove code not used

Signed-off-by: dab246 <tdvu@linagora.com>
(cherry picked from commit a935c960274102609fcb0edfc91556ef36137e7b)

lib/features/thread/presentation/thread_controller.dart

@@ -1199,18 +1199,6 @@ class ThreadController extends BaseController with EmailActionController {
     return DismissDirection.startToEnd;
   }
 
-  bool get inboxMailboxSelected => mailboxDashBoardController.selectedMailbox.value?.isInbox == true;
-
-  bool get systemBackGesturesEnable => inboxMailboxSelected && !mailboxDashBoardController.isDrawerOpen;
-
-  void backButtonPressedCallbackAction(BuildContext context) {
-    if (mailboxDashBoardController.isDrawerOpen) {
-      mailboxDashBoardController.closeMailboxMenuDrawer();
-    } else {
-      mailboxDashBoardController.openDefaultMailbox();
-    }
-  }
-
   void scrollToTop() {
     if (listEmailController.hasClients) {
       listEmailController.animateTo(0, duration: const Duration(milliseconds: 500), curve: Curves.fastOutSlowIn);